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11.
Gyula Dekany Karen Wright Peter Ward Istvan Toth 《Journal of carbohydrate chemistry》2013,32(4):383-398
Abstract Sialyl Lewis X (SLex) analogs 2a and 2b were synthesised, where the N-acetyl-D-glucose and the D-galactose units of SLex 1 were replaced with an alkyl and a heteroalkyl spacer. Sulphate ester 6i was also synthesised from alcohol 6b and chlorosulphonic acid. A novel promoter, silver mercaptoethanesulphonate, was used to synthesise α-sialosides 2c. 7b and 7c. 相似文献
12.
Structural Chemistry - 相似文献
13.
Tibor Kelen Tibor Kelen Lajos Balogh Istvan Majoros Gyorgy Deak 《Macromolecular Symposia》1993,67(1):325-338
The possibilities of increasing the livingness in cationic isobutylene polymerizations has been investigated. It has been assumed that the living chain-end is polarized but non-dissociated and relatively stable, therefore, i) shifting of the dissociation equilibrium by adding salts with common or non-common anion in excess, and ii) increasing of the stability of the chain-end by complexing it with electrondonors, may increase the livingness of the system. Indeed, the addition of n-Bu4NCl or n-Bu4NI to systems with BCl3 or TiCl4 coinitiators, as well as the addition of dimethyl sulphoxide as electrondonor in a broad concentration range, improved the living character. The possibility of complexation of the chain-end by the monomer has also been supported 相似文献
14.
Eva Hoffmann GyÖrgy Marko-Varga Istvan Csiky Jan Årke JÖnsoon 《International journal of environmental analytical chemistry》2013,93(1-3):161-171
Abstract A three-column ion chromatographic system for the removal of humic substances from natural waters, and subsequent on-line concentration and determination of nitrate and sulfate using non-suppressed ion chromatography is presented. Humic substances are removed using disposable adsorption columns packed with chemically bonded amine silica material. The sample is directly transfered to an ion exchange column where the anions are concentrated ca 10 times. After reversing the flow, the ions are transferred to a third column where they are separated and quantified. The detection limit is less than 1 mg L?1 of nitrate or sulfate in water containing 45mgL?1 of humic acid. 相似文献
15.
16.
Experiments were carried out on arrays of chaotic electrochemical oscillators to which global coupling, periodic forcing, and feedback were applied. The global coupling converts a very weakly coupled set of chaotic oscillators to a synchronized state with sufficiently large values of coupling strength; at intermediate values both intermittent and stable chaotic cluster states occur. Cluster formation and synchronization were also obtained by applying feedback and forcing to a moderately coupled base state. The three cases differ, however, in other details. The feedback and forcing also produce periodic cluster states and more than two clusters. Configurations of two (chaotic) clusters and two, three, or four (periodic) clusters were observed. (c) 2002 American Institute of Physics. 相似文献
17.
Recently, linear programming problems with special structures have assumed growing importance in mathematical programming.
It is well known that exploiting network structures within linear programs can lead to considerable improvement of the computational
solution of large-scale linear programming problems. A linear program is said to contain an embedded network structure provided
that some subset of its constraints can be interpreted as specifying conservation of flow. If a column of the constraint matrix
has at most two non-zeros, then it leads to embedded generalized network structure and if these non-zeros are unit elements
and of opposite signs, then it leads to embedded pure network structure.
In this paper, we are concerned with algorithms for detecting embedded pure network structures within linear programs. The
network extraction methods are presented in two groups. The first group covers deletion and addition based algorithms and
the second group covers GUB based algorithms. We have extended the GUB based algorithm appearing in the second group by introducing
Markowitz merit count approach for exploiting matrix non zeros. A set of well known test problems has been used to carry out
computational experiments which show that our extensions to the GUB based algorithms give better results than the algorithms
reported earlier. 相似文献
18.
Regis D. Gougeon Dr. Marianna Lucio Arnaud De Boel Moritz Frommberger Dr. Norbert Hertkorn Dr. Dominique Peyron Dr. David Chassagne Dr. François Feuillat Dr. Philippe Cayot Prof. Andrée Voilley Prof. Istvan Gebefügi Dr. Philippe Schmitt‐Kopplin Priv.‐Doz. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(3):600-611
A non‐targeted, ultra‐high‐resolution mass spectrometric, direct analysis of oak‐wood extracts from two species (Quercus robur L. and Quercus petraea Liebl.) from three French forests, and of a wine aged in barrels derived therefrom has been performed to identify families of metabolites that could discriminate both the species and the geographical origin of woods. From 12 T ultra‐high‐resolution Fourier transform ion cyclotron resonance mass spectra of wood extracts, hundreds of mass signals were identified as possible significant biomarkers of the two species, with phenolic and carbohydrate moieties leading the differentiation between Q. robur and Q. petraea, respectively, as corroborated by both FTMS and NMR data. For the first time, it is shown that oak woods can also be discriminated on the basis of hundreds of forest‐related compounds, and particular emphasis is put on sessile oaks from the Tronçais forest, for which sugars are significantly discriminant. Despite the higher complexity and diversity of wine metabolites, forest‐related compounds can also be detected in wines aged in related barrels. It is only by using these non‐targeted analyses that such innovative results, which reveal specific chemodiversities of natural materials, can be obtained. 相似文献
19.
Juvancz Zoltan Bodane-Kendrovics Rita Beleznay Peter Erdelyi Istvan Klujber-Mohr Maria 《Chromatographia》2010,71(1):125-128
1,4-Dichlorobenzene is a frequently used lavatory deodorant although it has strong endocrine disrupting and potential carcinogenic effects. A large amount (approximately 15,000 tonnes annually worldwide) of this compound is released into the environment. This paper deals with the determination of 1,4-dichlorobenzene in a variety of environmental matrices. Various extraction and concentration methods such as charcoal absorbtion tubes and headspace sampling were applied. Sensitive and selective ion monitoring GC-MS measurements were used for determination. Significant concentrations of the compound have been identified in lavatory air, waste water, waste water sludge and human breast milk.
相似文献20.
In this paper, we present three new mathematical techniques for evaluating the predictive skills of structure-activity experts. The question addressed in this paper is how to evaluate the predictive ability of structure-activity experts in identifying the most active compounds of a set of drug candidates. The three proposed mathematical techniques are based on the Phi-square Distance, the Rank Comparison, and the Shuffle method, respectively. They have been used to evaluate the performance of a new computer system and three human experts in predicting the antibacterial potencies of a series of chemical compounds in five different biological tests. The expert system, an artificial intelligence structure-activity program called MULTICASE, performed significantly better than one of the human experts and somewhat better than the other two.On leave from the Department of General and Analytical Chemistry, Technical University of Budapest, Szt. Gellert ter 4, 1111 Budapest, Hungary. 相似文献